Are hub motors worse?

ESK8 Electronics
21

Hub motors suffer from inefficient drive ratios. You can hide this a little by using larger motors but your battery range will still suffer.

One reason why range suffers so much with hub motors is they are dealing with much higher stall forces than a gear reduction drive and more energy is lost as heat because of this during acceleration.

Another performance drawback is poor riding characteristics due to the limited amount of urethane on a true hub motor. The best wheels available have high rebound urethane paired with a flexible but firm core. A thin band of urethane around a rigid aluminum core is not going to perform anywhere near as well as a modern longboard wheel.

9 Likes
22

Doesn’t halving the kV like they do in hub motors essentially have the same effect as using a 2:1 drive ratio though?

23

Hub can also be very efficient if its driven close to its top rpm. However the efficiency gets reduced if the Hub spins with load over certain period of time (heat is building up). So at this very moment big hub motors like the one for ebike are really really good, but doesn’t seems to be good yet for an eboard (smaller than 5inch for an hour non-stop ride).

24

in theory yes. in practice low kv hubs are only starting to show up…

also since you wrap the motor in urethane and close up most of the air flow you have to deal with heat alot more with out the added mass and crazy high running rpm that a belt drive would have…

what it really comes down to is what kind of ride you want. belt is great for hills and crazy torque. hubs are simple. reliable. smooth. stealth.

25

But I want both :cry:

26

you can have both. it just gets expensive with dual/quad hubs… :joy::money_mouth:

27

So throwing this out there, would a hub motor with a pneumatic tire be at all practical? You have all the cushioning you need, no worry of thin urethane affecting the feel of the ride but I have the feeling the stall forces make it not possible or highly impractical.

1 Like
28

This is already done on electric scooters (and bikes technically!). Maybe someone can throw 4 scooter hubs on a board.

29

Just a thought, do carvons have better cooling than hub motors?

30

Oh yes that true! Didn’t even consider this outside the scope of longboarding. But those seem like much larger hub motors than what we currently have on boards

31

Yea, you’ll probably need the larger hub motors in order to drive pneumatics.

32

This is technically not true. Yes, Pulleys & Belts are great for multiplying motor torque, however, there is a limit to how much torque can be transferred by a belt drive. The belt is a torque bottleneck & also introduces many other design constraints & maintenance requirements.

When it comes to performance what is most important is torque at the wheel. This is why car enthusiasts & engine tuners always measure torque at the wheel with the car/bike strapped to a dyno, the dyno results represent total power minus transmission losses.

For example, Take a 9mm wide, 5mm pitch belt drive on a normal satellite drive train on an electric skateboard, you can transfer a max of 2Nm of torque into the wheel at 1000rpm.

Pasted image1035×773 225 KB

After that, you get belt slipping & reduced service life of your drive train (I dont have simulations for brake force, I believe peak torque for braking is actually much greater so you get more slipping). It also doesn’t really matter if you have an idler either, eventually you reach the torque transfer limits. In fact, the only way to increase the torque transfer is to increase the size of the motor pulley & your belt width. This reduces reduction & increases losses, eventually you end up nearly-having a direct drive system! However, you still have transmission losses due to belt friction/resistance.

Now, Install a hub motor & the power is already at the wheel, with the new R-SPEC GHOST Direct Drive simulations, we see (3X) 6nm of torque at the wheel at 1000RPM - the torque is also delivered at 55% HIGHER BOARD SPEED!

When you develop a motor for a specific application you will always get better results than when adapting a motor with a transmission system. Transmission systems are just not needed in the new era of motor technology, they are inefficient at transferring torque, they are more complex to assemble, prone to damage from debris, need regular maintenance & have a higher running cost due to the lifespan of the belts.

Direct drive systems are appearing everywhere now… there is a reason for this!

blob.jpg865×302 27.1 KB

2 Likes
33

Looking forward to seeing your dyno tests and your raptor 1 vs raptor 2 videos. When do you think you can make that happen?

34

it will happen for sure

35

Are the hub motors offered on Enertion website the same ones that will come on the Raptor 2?

36

Where do you see these motor on enertion web site ?

37

You must smoke some really good weed. :wink:

4 Likes
38

There aren’t any hub motors on the enertion site. They aren’t being sold separately yet and haven’t even been released. They will be sold with the Raptor 2.

39

I think the title of this thread should be changed to “Are hub motors worse?”

40

Thats sound pretty impressive. I can wait to see this thing in action! I’m really digging the new look you took with this one. Is the majority of this improvement due to the addition of Hall sensors or are there other factors that you attribute that to?